There is moiré in the blue shirt in the RAW file, but not in the SOOC JPG. (Take a look, e.g., at the area between his camera and his vest after zooming in.) Even with Markesteijn 3-pass demosaic + five times color smoothing I still see moiré.

I wanted to find out whether this is a Fujifilm-related issue or a Darktable-related issue, so I asked a friend to open the RAW file in Lightroom (version 5.7.64) and export a full resolution JPG. (Since all my computers rum Linux, I do not access to LR.) Here is the resulting JPG:

It seems that one needs to use very aggressive denoise profiled (wavelet + color) and defringe settings to get rid of the moiré, as noted by Marc Cousin in the darktable-users mailing list. Nonetheless, that has side effects. I reproduce Marc's latest message:

History

So moire is an expected issue in digital photography, especially with sensors that have the low pass filter removed.

Even though Fuji advertises it's X-Trans to be better Moire resistant, there has never been any verifiable proof to this statement. So there is no real reason to think this is actually the case. Fuji has a long history of over-marketing over-complicated sensor designs that often aren't really that much better than a traditional Bayer to begin with.

The out of camera / lightroom images aren't too relevant, as this shows the result of a full imaging pipeline, they may just be employing a general moire reduction algorithm (whatever it may be).

Other tools implementing Markesteijn demosaic for X-Trans show exactly the same moire pattern, so our Markesteijn implementation doesn't seem to have any Darktable specific bugs. It might be interesting to hear Frank Markesteijn opinion on this matter though.

Were there any Fujifilm-specific settings enabled when the taken was taken, like a shot ISO in the EXIF != actual ISO that was used to take the picture?IIRC Fujifilm only records the intended ISO, not the actual one, so in such case dt uses noiseprofile for wrong iso.

Were there any Fujifilm-specific settings enabled when the taken was taken, like a shot ISO in the EXIF != actual ISO that was used to take the picture?IIRC Fujifilm only records the intended ISO, not the actual one, so in such case dt uses noiseprofile for wrong iso.

Exif isn't the real ISO: this was taken with DR Auto. The camera chose DR-200, so it means that the ISO displayed is the effective ISO in the highlights. Here, for instance, it is DR-200 and 400 ISO in exif.

It means the picture is taken with the sensor at 200 ISO, underexposed by one stop. To have a correctly exposed picture, in Darktable, you have to set exposure to +1. In order to get a similar rendering to the camera, you also have to either play with shadows and highlights, or modify a base curve or tone curve, for instance.

Anyway, the effective ISO is 400 in this picture, for the highlights at least. And even with the 200-ISO profile, I get the same artifacts. Less of them, of course, as denoising is less agressive, but I still have them. And of course, the moire is stronger, and other color noise too.

Exif isn't the real ISO: this was taken with DR Auto. The camera chose DR-200, so it means that the ISO displayed is the effective ISO in the highlights. Here, for instance, it is DR-200 and 400 ISO in exif.

It means the picture is taken with the sensor at 200 ISO, underexposed by one stop. To have a correctly exposed picture, in Darktable, you have to set exposure to +1. In order to get a similar rendering to the camera, you also have to either play with shadows and highlights, or modify a base curve or tone curve, for instance.

Anyway, the effective ISO is 400 in this picture, for the highlights at least. And even with the 200-ISO profile, I get the same artifacts. Less of them, of course, as denoising is less agressive, but I still have them. And of course, the moire is stronger, and other color noise too.